1. Field of the Invention
This invention relates generally to the field of material transport systems and particularly to a web transport system.
Material transport systems move various types of material from one location to another. Some material transport systems are used to move thin materials. An example of a thin material is a filmstrip or filmstrip and paper carrier combination or web.
When a filmstrip is printed for the first time (first order), the various 24 and 36 exposure filmstrips are joined end to end to form a continuous constant width filmstrip roll. In order to make photographic printers more efficient during reorder operations, the various frames of a filmstrip, that a customer wants reprinted are attached to a paper carrier. The paper carrier forms a roll containing many frames, that are randomly attached to one side of the paper carrier. Thus, in certain roll locations there will be filmstrip and a paper carrier and in other roll locations there will only be a paper carrier. Hence, the width of the filmstrip paper carrier combination varies. The paper carrier filmstrip combination is able to be rapidly moved through the printer. Whereas, if the filmstrip was not connected to a paper carrier, individual frames on four frame filmstrips would have to be moved through the printer.
Rollers may be used to guide a first order filmstrip by contacting either edge of the filmstrip. However, if the filmstrip is connected to a paper carrier, the guide roller may only contact the paper carrier portion of the roll, since the filmstrip segments are too flimsy and are intermittent.
The lateral position of the filmstrip and the filmstrip paper carrier combination needs to be accurately controlled to permit the bar code on the filmstrip and/or the code on the paper carrier to be read. Devices contained within the printer use the information contained in the above codes to set or adjust various photographic printer parameters to produce better quality prints. Thus, precise lateral placement of the filmstrip and filmstrip paper carrier combination is necessary for proper scanning, printing and transport operations.
One of the methods utilized by the prior art to obtain accurate lateral positioning of a filmstrip and paper carrier combination was to urge one edge of the paper carrier against a guiding member having a fixed lateral position. The filmstrip paper carrier combination was very thin. Thus, the filmstrip paper carrier combination did not support significant lateral locating forces without buckling.
Buckling caused inaccurate edge reading of the filmstrip. The buckling of the filmstrip and paper carrier combination was reduced by increasing the lateral column strength of the paper carrier. The lateral column strength of the paper carrier was increased by curving the paper carrier around a transverse axis. The above transverse axis curvature required a change in the filmstrip paper carrier direction from before the guide to after the guide. Thus, additional rollers were needed to change the direction of travel of the filmstrip paper carrier combination to accurately laterally position the filmstrip and paper carrier.
If the filmstrip and filmstrip paper carrier combination travels a large distance, additional rollers are needed to accurately control the lateral position of the filmstrip and the filmstrip paper carrier combination.
If the speed of the filmstrip moving through the photographic printer was increased above 18 inches per second, prior art rollers had difficulty in accurately controlling the lateral position of the filmstrip. The prior art difficulty in accurately controlling the lateral position of the filmstrip was amplified on reorder.